A major obstacle to the development of vaccines against viruses, particularly those with multiple serotypes or a high rate of mutation, against which elicitation of neutralizing and protective immune responses is desirable, is the diversity of the viral external proteins among different viral isolates or strains. Since cytotoxic T-lymphocytes (CTLs) in both mice and humans are capable of recognizing epitopes derived from conserved internal viral proteins [J. W. Yewdell et al., Proc. Natl. Acad. Sci. (USA) 82, 1785 (1985); A. R. M. Townsend, et al., Cell 44, 959 (1986); A. J. McMichael et al., J. Gen. Virol. 67, 719 (1986); J. Bastin et al., J. Exp. Med. 165, 1508 (1987); A. R. M. Townsend and H. Bodmer, Annu. Rev. Immunol. 7, 601 (1989)], and are thought to be important in the immune response against viruses [Y.-L. Lin and B. A. Askonas, J. Exp. Med. 154, 225 (1981); I. Gardner et al., Eur. J. Immunol. 4, 68 (1974); K. L. Yap and G. L. Ada, Nature 273, 238 (1978); A. J. McMichael et al., New Engl. J. Med. 309, 13 (1983); P. M. Taylor and B. A. Askonas, Immunol. 58, 417 (1986)], efforts have been directed towards the development of CTL vaccines capable of providing heterologous protection against different viral strains.
It is known that CTLs kill virally-infected cells when their T cell receptors recognize viral peptides associated with MHC class I and or class II molecules. These peptides can be derived from endogenously synthesized viral proteins, regardless of the protein's location or function within the virus. By recognition of epitopes from conserved viral proteins, CTLs may provide heterologous protection.
Many infectious disease causing agents can, by themselves, elicit protective antibodies which can bind to and kill, render harmless, or cause to be killed or rendered harmless, the disease causing agent and its byproducts. Recuperation from these diseases usually results in long-lasting immunity by virtue of protective antibodies generated against the highly antigenic components of the infectious agent.
Protective antibodies are part of the natural defense mechanism of humans and many other animals, and are found in the blood as well as in other tissues and bodily fluids. It is the primary function of most vaccines to elicit protective antibodies against infectious agents and/or their byproducts, without causing disease.
Most efforts to generate CTL responses have either used replicating vectors to produce the protein antigen within the cell [J. R. Bennink et al., ibid. 311, 578 (1984); J. R. Bennink and J. W. Yewdell, Curr. Top. Microbiol. Immunol. 163, 153 (1990); C. K. Stover et al., Nature 351, 456 (1991); A. Aldovini and R. A. Young, Nature 351, 479 (1991); R. Schafer et al., J. Immunol. 149, 53 (1992); C. S. Hahn et al., Proc. Natl. Acad. Sci. (USA) 89, 2679 (1992)], or they have focused upon the introduction of peptides into the cytosol [F. R. Carbone and M. J. Bevan, J. Exp. Med. 169, 603 (1989); K. Deres et al., Nature 342, 561 (1989); H. Takahashi et al., ibid. 344, 873 (1990); D. S. Collins et al., J. Immunol. 148, 3336 (1992); M. J. Newman et al., ibid. 148, 2357 (1992)]. Both of these approaches have limitations that may reduce their utility as vaccines. Retroviral vectors have restrictions on the size and structure of polypeptides that can be expressed as fusion proteins while maintaining the ability of the recombinant virus to replicate [A. D. Miller, Curr. Top. Microbiol. Immunol. 158, 1 (1992)], and the effectiveness of vectors such as vaccinia for subsequent immunizations may be compromised by immune responses against vaccinia [E. L. Cooney et al., Lancet 337, 567 (1991)]. Also, viral vectors and modified pathogens have inherent risks that may hinder their use in humans [R. R. Redfield et al., New Engl. J. Med. 316, 673 (1987); L. Mascola et al., Arch. Intern. Med. 149, 1569 (1989)]. Furthermore, the selection of peptide epitopes to be presented is dependent upon the structure of an individual's MHC antigens and, therefore, peptide vaccines may have limited effectiveness due to the diversity of MHC haplotypes in outbred populations.
Benvenisty, N., and Reshef, L. [PNAS 83, 9551-9555, (1986)] showed that CaCl2 precipitated DNA introduced into mice intraperitoneally (i.p.), intravenously (i.v.) or intramuscularly (i.m.) could be expressed. The intramuscular (i.m.) injection of DNA expression vectors in mice has been demonstrated to result in the uptake of DNA by the muscle cells and expression of the protein encoded by the DNA [J. A. Wolff et al., Science 247, 1465 (1990); G. Ascadi et al., Nature 352, 815 (1991)]. The plasmids were shown to be maintained episomally and did not replicate. Subsequently, persistent expression has been observed after i.m. injection in skeletal muscle of rats, fish and primates, and cardiac muscle of rats [H. Lin et al., Circulation 82, 2217 (1990); R. N. Kitsis et al., Proc. Natl. Acad. Sci. (USA) 88, 4138 (1991); E. Hansen et al., FEBS Lett. 290, 73 (1991); S. Jiao et al., Hum. Gene Therapy 3, 21 (1992); J. A. Wolff et al., Human Mol. Genet. 1,363 (1992)]. The technique of using nucleic acids as therapeutic agents was reported in WO90/11092 (Oct. 4, 1990), in which naked polynucleotides were used to vaccinate vertebrates.
Recently, the coordinate roles of B7 and the major histocompatibility complex (MHC) presentation of epitopes on the surface of antigen presenting cells in activating CTLs for the elimination of tumors was reviewed [Edgington, Biotechnology 11, 1117-1119, 1993]. Once the MHC molecule on the surface of an antigen presenting cell (APC) presents an epitope to a T-cell receptor (TCR), B7 expressed on the surface of the same APC acts as a second signal by binding to CTLA-4 or CD28. The result is rapid division of CD4+ helper T-cells which signal CD8+ T-cells to proliferate and kill the APC.
It is not necessary for the success of the method that immunization be intramuscular. Thus, Tang et al., [Nature, 356, 152-154 (1992)] disclosed that introduction of gold microprojectiles coated with DNA encoding bovine growth hormone (BGH) into the skin of mice resulted in production of anti-BGH antibodies in the mice. Furth et al., [Analytical Biochemistry, 205, 365-368, (1992)] showed that a jet injector could be used to transfect skin, muscle, fat, and mammary tissues of living animals. Various methods for introducing nucleic acids was recently reviewed [Friedman, T., Science, 244, 1275-1281 (1989)]. See also Robinson et al., [Abstracts of Papers Presented at the 1992 meeting on Modern Approaches to New Vaccines, Including Prevention of AIDS, Cold Spring Harbor, p92], where the im, ip, and iv administration of avian influenza DNA into chickens was alleged to have provided protection against lethal challenge. Intravenous injection of a DNA: cationic liposome complex in mice was shown by Zhu et al., [Science 261, 209-211 (Jul. 9, 1993); see also WO93/24640, Dec. 9, 1993] to result in systemic expression of a cloned transgene. Recently, Ulmer et al., [Science 259, 1745-1749, (1993)] reported on the heterologous protection against influenza virus infection by injection of DNA encoding influenza virus proteins.
Wang et al., [P.N.A.S. USA 90, 4156-4160 (May, 1993)] reported on elicitation of immune responses in mice against HIV by intramuscular inoculation with a cloned, genomic (unspliced) HIV gene. However, the level of immune responses achieved was very low, and the system utilized portions of the mouse mammary tumor virus (MMTV) long terminal repeat (LTR) promoter and portions of the simian virus 40 (SV40) promoter and terminator. SV40 is known to transform cells, possibly through integration into host cellular DNA. Thus, the system described by Wang et al., is wholly inappropriate for administration to humans, which is one of the objects of the instant invention.
WO 93/17706 describes a method for vaccinating an animal against a virus, wherein carrier particles were coated with a gene construct and the coated particles are accelerated into cells of an animal.
Recent efforts to develop subunit vaccines for herpes simplex virus (HSV) have focused on novel expression and presentation of viral antigens; especially the viral glycoproteins. [for review see Burke, R. L., 1993, Sem. In Virol., 4, pp.187-197] Recombinant HSV glycoproteins expressed by a variety of systems including yeast (Kino., Y. C. et al., 1989, Vaccine, 7, pp.155-160), insect cells (Ghiasi, H. et al., 1991, Arch.Virol., 121, pp.163-178), and mammalian cells (Burke, R. L., 1991, Rev.Infect.Dis., 13 S906-S911; Lasky, L. A., 1990, J.Med.Virol., 31, pp.59-61) have been shown to elicit protective immunity in animal models. Clinical trials of a recombinant HSV-2 glycoprotein D (gD) produced in Chinese hamster ovary cells have shown that the vaccine induces an antibody response in naive individuals and stimulates the pre-existing response in both HSV-1 and HSV-2 seropositive individuals. (Straus, S. E. et al., 1993, J.Infect.Dis., 167, pp.1045-1052)
An alternate approach to subunit vaccination has been the use of live virus vectors for delivery of HSV antigens. Vaccinia-HSV recombinants expressing gD (Aurelian, L. et al., 1991, Rev.Infect.Dis., 13, S924-S930; Rooney, J. F. et al., 1991, Rev.Infect.Dis., 13, S898-S903; Wachsman, M. et al., 1992, Vaccine, 10, pp.447-454) gB (Rooney, J. F. et al., supra), gL and gH (Browne, H. et al., 1993, J.Gen.Virol., 74, pp.2813-2817) have successfully protected animals from HSV challenge. Vaccination by infection with recombinant adenovirus expressing HSV gB elicits a protective immune response in mice. (Ghiasi, H., supra; McDermott, M. R., 1989, Virology, 169, pp.244-247) It is well documented that anti-gD antibodies can protect against HSV infection whether elicited by immunization with native protein (Long, D. et al., 1984, Infect.Immun., 43, pp.761-764) recombinantly expressed protein (Burke, R. L., supra; Stanberry, L. R. et al., 1987, J.Infect.Dis., 155, pp.914-920; Straus, S.E., supra) peptides derived from gD (Eisenberg, R. J. et al., 1985, J.Virol., 56, pp.1014-1027) or transferred passively (Dix, R. D. et al., 1981, Infect.Immun., 34, pp.192-199; Ritchie, M. H. et al., 1993, Investigative Ophthalmology and Visual Sciences, 34, pp.2460-2468).
Studies by Wolff et al. (supra) originally demonstrated that intramuscular injection of plasmid DNA encoding a reporter gene results in the expression of that gene in myocytes, at and near the sight of injection. Recent reports demonstrated the successful immunization of mice against influenza by the injection of plasmids encoding influenza A hemagglutinin (Montgomery, D. L. et al., 1993, Cell Biol., 12, pp.777-783), or nucleoprotein (Montgomery, D. L. et al., supra; Ulmer, J. B. et al., 1993, Science, 259, pp.1745-1749). The first use of DNA immunization for a herpes virus has been reported (Cox et al., 1993, J.Virol., 67, pp.5664-5667). Injection of a plasmid encoding bovine herpesvirus 1 (BHV-1) glycoprotein g IV gave rise to anti-g IV antibodies in mice and calves. Upon intranasal challenge with BHV-1, immunized calves showed reduced symptoms and shed substantially less virus than controls. The ability of HSV glycoprotein D to elicit a protective immune response in mice (Long, D. et al., supra) and guinea pigs (Stanberry, L. R. et al., supra; Stanberry, L. R. et al., 1989, Antiviral.Res., 11, pp.203-214) is well documented.